The present invention provides novel genes, proteins, and uses thereof including, methods for diagnosing and treating cancer, particularly metastatic cancer.
Most eukaryotic cells (execptions include red blood cells and adult muscles) contain high concentrations, i.e., up to .about.250 .mu.mol/l, of momomeric actin. How such actin remains unpolymerized in the cytoplasm has remained a problem in cell biology (Nachmiar, V., Current Opinion in Cell Biology, 1993, 5:56). Profilin, originally thought to be the actin-sequestering protein, is not present in sufficient amounts to account for more than part of the monomeric actin levels observed. Recently, an actin-sequestering 5 kD peptide was discovered in high concentration in human platelets (Safer, et al., Proc. Natl. Acad. Sci USA 1990 87:2536-2540) and shown to be identical to a previously known peptide (Safter, et al., J. BIol. Chem., 1991, 268:4029-4032) originally thought to be the thymic hormone, thymosin .beta..sub.4 (T.beta..sub.4) (D. Safer, J. Muscle Res. Cell Motil, 1992.13:269-271). A detailed kinetic study of the interaction of T.beta..sub.4 and actin (Weber, et al., Biochemistry 1992, 31:6179-6185)), together with other studies (Yu, et al., J. BIol. Chem., 1993, 268:502-509 and Cassimelds, et al., J. Cell Biol., 1992, 119:1261-1270) support the hypothesis that T.beta..sub.4 and T.beta..sub.10 function primary as G-actin buffers. Unpublished data (E. Hannappel) extend the function to several other, .beta. thymosins. T.beta..sub.4 has also been shown to inhibit nucleotide exchange by actin, whereas profilin increases the rate of exchange (Coldschmidt-Clermont, et al., Mol. Cell Bio., 1992, 3:1015-1025).
All vertebrates studied contain one or often two, .beta.-thymosins. Thus, the members of the .beta.-thymosin family are believed to be important in all species. Three new family members (Low, et al., Arch. Biochem. Biophys., 1992, 293:32-39 and Schmid, B., Ph.D Thesis, University of Tubingen 1989) have been found in perch, trout and in sea urchin, the first non-vertebrate source. The sequences are well conserved suggesting that actin sequestration is probably a property of all .beta.-thymosins. However, when T.beta..sub.4 was discovered and its sequence first determined in 1981 (Low, et al., Proc. Natl. Acad. Sci., USA 1981, 78:1162-1166), data were presented that suggested two extracellular functions (Low, et al. supra and Rebar, et al., Science 1981, 214:669-671). Two recent papers indicate a different and unexpected effect of a tetrapeptide which may be derived from the amino terminus of T.beta..sub.4.
Several reports demonstrate regulation of T.beta..sub.4 or T.beta..sub.10 synthesis at the transcriptional or translational level. An interferon-inducible gene (Cassimelds, et al., J. Cell. Biol. 1992, 119:1261-1270 and Sanders, et al., Proc. Natl. Acad. Sci. USA 1992, 89:4678-4682) is identical to the cDNA of human T.beta..sub.4, and there are several genes for T.beta..sub.4 in humans. (Clauss, et al., Genomies 1991, 9:75-180 and Gomez-Marquez, et al., J. Immunol. 1989, 143:2740-2744)
It would be desirable to identify new members of the .beta.-thymosin family, particularly in humans.
Bao and Zetter reported in an abstract presented at the American Association for Cancer Research annual meeting (Mar. 18-22, 1995) the differential expression of a novel mRNA expressed in high-metastatic rat tumor cell lines, but not in a low metastatic variant. cDNA was isolated and was reported to encode a protein with 68% identity to the rat thymosin,64. However, the nucleotide sequence and the deduced amino acid sequence were not reported.